This invention is an improvement on the apparatus shown in prior U.S. Pat. No. 4,871,182 to Russell G. Altherr et al, the disclosure of which is incorporated herein by reference.
Fifth wheel devices include a plate which supports the forward bed plate of a trailer. A king pin is fixed to the trailer bed plate and extends into a center opening of the fifth wheel plate. Fifth wheels have included a pivotally mounted jaw to engage and hold the king pin against horizontal withdrawal. Normally, the jaw closes and is locked on the king pin as the tractor and trailer are brought together. However, there is also a mechanism provided to unlock the jaw to permit horizontal release of a king pin and allow separation of tractor and trailer when the trailer is stationary and the tractor is powered forward. That mechanism usually is operable manually by a driver and includes safeguards so as to avoid accidental release. While there have been earlier designs for automatically unlatching fifth wheels, for example see U.S. Pat. No. 2,471,854 to Bies et al, experience with over the road hauling during the last several decades has developed an abundance of caution against automatic operation of fifth wheels and, largely for reasons of safety, the industry has disdained powered release mechanisms. Thus modern over the road fifth wheels, such as that shown in U.S. Pat. No. 4,871,182, have incorporated locking features that are solely manually operable from outside the tractor cab and have not been regarded as suitable for powered operation. However, as trucks have tended to become larger in size and incorporate aerodynamic design features it has become more difficult to reach the operating mechanism and this problem is exacerbated for persons of small stature. Furthermore even for tall persons manual operation has caused soiling and tearing of clothing and, for some, may have contributed to back strains and the like.